Creeping temp gauge

dja4260

dja4260

Joined
May 16, 2011
Messages
1,518
Location
Greenville, SC via Chicago, IL
I was sitting at drive through today. I glanced down at the the temp gauge and it was creeping up from 205-220, then repeatedly dropped back to 205. I turned the heat on full blast with the hope to get my food and pull over as the lady in front of me ordered the entire menu. The gauge never moved past 220, then went back it it's normal 205 degrees.... I drove immediately to pick up a new thermostat and some antifreeze...

05 Suburban with 69k miles. The radiator has been replaced within the past 3 years, water pump is original. I'm going to replace the thermostat tomorrow.

Anything else that comes to mind?
 
Make sure the belts and fan clutch are OK , or the electric fan , if that is what it has .

Sounds like you have started down the correct path . Best of luck to you .
 
First before buying anything wait until cold and check the coolant level in the radiator (if it is a non-pressurized expansion tank system).

Assuming it's not short of coolant, overheating only when idling sitting still is going to be fan related. Possibly the thermostat that turns on the electric fan has become unreliable and turned it on late.
 
I vote on a bad fan clutch.

My grandparents used to have an 02' Trailblazer and it would creep way up at idle and cool down on the highway. A/C performance was poor too. Once it got a new fan clutch it ran cool and the A/C was great.
 
I suspect one of your electric cooling fans is not opperating. Pretty sure that's a dual electric fan system? I'm not a Subaru guy so I don't know for sure, but it sounds like maybe the low temp fan is not working and the second is not coming on until the ECU sees 220f.

A typical cooling strategy is that the ECU will command one of the fans on at a certain temp and then the second one at a higher temp. Since the low temp commanded fan is used more often, a lot of times that's the one that goes bad first.
 
Airflow issue. Either plugged fins on radiator, condenser or the fan is not working. Putting on the a/c should kick the fans on full time or pulling off the connector on the coolant temperature sensor for the ECU will turn on the fans on many vehicles.
 
Dja4260. Would you please open your hood and take a picture of your fan to confirm if you have a clutch type fan or an electric fan? You mentioned “ fans,motors and clutches” You are mixing up two different systems. Clutch systems do not have fan motors and fan motor systems do not have clutches. Thanks.
 
Last edited:
If you have access to a scan tool with diagnostics functions that can command on the fans, that would be the best way to confirm a problem with the fans before you shoot parts at it. You might have a bad fan motor, broken wiring, a bad relay or even a blown fuse.

You could try to use jumper wires to test each fan with 12 volts to verify that they spin to see if the problem is the motor or somewhere else. Also, the fan that you linked to is for a GM truck. Are you sure that's the right one? I think most Subaru's of that era had two individual fans that can be replaced separately?
 
I've been very busy and haven't dived into this yet. Yesterday I went for a ride. With the AC on, both fans were operating and the temp was stable. With the AC OFF, the temp gauge did move slightly. I popped the hood and both fans were not on. I'll spend some more time watching the fans with the AC OFF and report back. I have no idea if the fans have a clutch or are electric. I also don't have access to a scan tool...
 
dja4260 said:
I've been very busy and haven't dived into this yet. Yesterday I went for a ride. With the AC on, both fans were operating and the temp was stable. With the AC OFF, the temp gauge did move slightly. I popped the hood and both fans were not on. I'll spend some more time watching the fans with the AC OFF and report back. I have no idea if the fans have a clutch or are electric. I also don't have access to a scan tool...
Click to expand...
The fans will always be on with the a/c. With the a/c off, the fans will turn on and off as needed.
 
The Low Speed Fans (Both run at 1/2 speed) come on at 226°F, They turn off at 219°F or run a minimum of 90 seconds. Your description sounds like normal operation to me with the A/C off & no airflow across the radiator. You can recalibrate the Fan vs ECT with tuning software.

This is a stock Fan vs ECT vs A/C pressure table for a 2005 Suburban 1500.......

qpEml1V.png
 
Last edited:
clinebarger said:
The Low Speed Fans (Both run at 1/2 speed) come on at 226°F, They turn off at 219°F or run a minimum of 90 seconds. Your description sounds like normal operation to me with the A/C off & no airflow across the radiator. You can recalibrate the Fan vs ECT with tuning software.

This is a stock Fan vs ECT vs A/C pressure table for a stock 2005 Suburban 1500.......

qpEml1V.png
Click to expand...

Yep. Normal operation, especially in 90*F ish ambient temperatures.
 
clinebarger said:
The Low Speed Fans (Both run at 1/2 speed) come on at 226°F, They turn off at 219°F or run a minimum of 90 seconds. Your description sounds like normal operation to me with the A/C off & no airflow across the radiator. You can recalibrate the Fan vs ECT with tuning software.

This is a stock Fan vs ECT vs A/C pressure table for a 2005 Suburban 1500.......

qpEml1V.png
Click to expand...

If this is normal operation, why would the temp gauge swing back and forth so drastically? Does this sound like a thermostat issue? It's a cheap part to replace...
 
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